Royal Caribbean, Princess, NCL, Carnival, or Disney? Which is best to work for?

Has anyone worked for Royal Caribbean, NCL, Carnival, Princess, or Disney Cruise Lines? I am considering applying for positions of Training Coordinator or Youth Counselor, and am trying to get reviews from others who have worked for different cruise lines.

My dream job would be getting on a ship that cruises around the world, such as some of the Princess ships, and not just one that hits the same ports over and over. Obviously, I know you can't choose your ship, but would you recommend certain lines over others? I worry more about Carnival and Disney being mainly short cruises vice some of the other lines which offer cruises much longer in length.

Also, maybe you can give me insight as to what life is like working in higher positions such as Staff vs Crew on ships. I think I would love being a Youth Counselor, but I am over 50, and don't know if there will be any people my age in the area we are confined to on the ship.